// Copyright 2022 jeff.li. and/or its affiliates.
// Taken from https://github.com/abseil/abseil-cpp/blob/master/absl/hash/internal/city.cc
//
// Copyright (c) 2011 Google, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
// CityHash, by Geoff Pike and Jyrki Alakuijala
//
// This file provides CityHash64() and related functions.
//
// It's probably possible to create even faster hash functions by
// writing a program that systematically explores some of the space of
// possible hash functions, by using SIMD instructions, or by
// compromising on hash quality.

#include <tbir/runtime/hash/base/config.h>
#include <tbir/runtime/hash/base/endian.h>
#include <tbir/runtime/hash/base/unaligned_access.h>
#include <tbir/runtime/hash/city_hash.h>

#include <string.h>  // for memcpy and memset
#include <algorithm>

namespace tbir::runtime::hash_internal {

#ifdef TBIR_IS_BIG_ENDIAN
#define uint32_in_expected_order(x) (base_internal::gbswap_32(x))
#define uint64_in_expected_order(x) (base_internal::gbswap_64(x))
#else
#define uint32_in_expected_order(x) (x)
#define uint64_in_expected_order(x) (x)
#endif

    static uint64_t Fetch64(const char *p) noexcept {
        return uint64_in_expected_order(TBIR_INTERNAL_UNALIGNED_LOAD64(p));
    }

    static uint32_t Fetch32(const char *p) noexcept {
        return uint32_in_expected_order(TBIR_INTERNAL_UNALIGNED_LOAD32(p));
    }

    // Some primes between 2^63 and 2^64 for various uses.
    static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
    static const uint64_t k1 = 0xb492b66fbe98f273ULL;
    static const uint64_t k2 = 0x9ae16a3b2f90404fULL;

    // Magic numbers for 32-bit hashing.  Copied from Murmur3.
    static const uint32_t c1 = 0xcc9e2d51;
    static const uint32_t c2 = 0x1b873593;

    // A 32-bit to 32-bit integer hash copied from Murmur3.
    static uint32_t fmix(uint32_t h) noexcept {
        h ^= h >> 16;
        h *= 0x85ebca6b;
        h ^= h >> 13;
        h *= 0xc2b2ae35;
        h ^= h >> 16;
        return h;
    }

    static uint32_t Rotate32(uint32_t val, int shift) noexcept {
        // Avoid shifting by 32: doing so yields an undefined result.
        return shift == 0 ? val : ((val >> shift) | (val << (32 - shift)));
    }

#undef PERMUTE3
#define PERMUTE3(a, b, c) \
  do {                    \
    std::swap(a, b);      \
    std::swap(a, c);      \
  } while (0)

    static uint32_t Mur(uint32_t a, uint32_t h) noexcept {
        // Helper from Murmur3 for combining two 32-bit values.
        a *= c1;
        a = Rotate32(a, 17);
        a *= c2;
        h ^= a;
        h = Rotate32(h, 19);
        return h * 5 + 0xe6546b64;
    }

    static uint32_t Hash32Len13to24(const char *s, size_t len) noexcept {
        uint32_t a = Fetch32(s - 4 + (len >> 1));
        uint32_t b = Fetch32(s + 4);
        uint32_t c = Fetch32(s + len - 8);
        uint32_t d = Fetch32(s + (len >> 1));
        uint32_t e = Fetch32(s);
        uint32_t f = Fetch32(s + len - 4);
        uint32_t h = len;

        return fmix(Mur(f, Mur(e, Mur(d, Mur(c, Mur(b, Mur(a, h)))))));
    }

    static uint32_t Hash32Len0to4(const char *s, size_t len) noexcept {
        uint32_t b = 0;
        uint32_t c = 9;
        for (size_t i = 0; i < len; i++) {
            signed char v = s[i];
            b = b * c1 + v;
            c ^= b;
        }
        return fmix(Mur(b, Mur(len, c)));
    }

    static uint32_t Hash32Len5to12(const char *s, size_t len) noexcept {
        uint32_t a = len, b = len * 5, c = 9, d = b;
        a += Fetch32(s);
        b += Fetch32(s + len - 4);
        c += Fetch32(s + ((len >> 1) & 4));
        return fmix(Mur(c, Mur(b, Mur(a, d))));
    }

    uint32_t CityHash32(const char *s, size_t len) noexcept {
        if (len <= 24) {
            return len <= 12 ? (len <= 4 ? Hash32Len0to4(s, len) : Hash32Len5to12(s, len))
                             : Hash32Len13to24(s, len);
        }

        // len > 24
        uint32_t h = len, g = c1 * len, f = g;

        uint32_t a0 = Rotate32(Fetch32(s + len - 4) * c1, 17) * c2;
        uint32_t a1 = Rotate32(Fetch32(s + len - 8) * c1, 17) * c2;
        uint32_t a2 = Rotate32(Fetch32(s + len - 16) * c1, 17) * c2;
        uint32_t a3 = Rotate32(Fetch32(s + len - 12) * c1, 17) * c2;
        uint32_t a4 = Rotate32(Fetch32(s + len - 20) * c1, 17) * c2;
        h ^= a0;
        h = Rotate32(h, 19);
        h = h * 5 + 0xe6546b64;
        h ^= a2;
        h = Rotate32(h, 19);
        h = h * 5 + 0xe6546b64;
        g ^= a1;
        g = Rotate32(g, 19);
        g = g * 5 + 0xe6546b64;
        g ^= a3;
        g = Rotate32(g, 19);
        g = g * 5 + 0xe6546b64;
        f += a4;
        f = Rotate32(f, 19);
        f = f * 5 + 0xe6546b64;
        size_t iters = (len - 1) / 20;
        do {
            uint32_t b0 = Rotate32(Fetch32(s) * c1, 17) * c2;
            uint32_t b1 = Fetch32(s + 4);
            uint32_t b2 = Rotate32(Fetch32(s + 8) * c1, 17) * c2;
            uint32_t b3 = Rotate32(Fetch32(s + 12) * c1, 17) * c2;
            uint32_t b4 = Fetch32(s + 16);
            h ^= b0;
            h = Rotate32(h, 18);
            h = h * 5 + 0xe6546b64;
            f += b1;
            f = Rotate32(f, 19);
            f = f * c1;
            g += b2;
            g = Rotate32(g, 18);
            g = g * 5 + 0xe6546b64;
            h ^= b3 + b1;
            h = Rotate32(h, 19);
            h = h * 5 + 0xe6546b64;
            g ^= b4;
            g = base_internal::gbswap_32(g) * 5;
            h += b4 * 5;
            h = base_internal::gbswap_32(h);
            f += b0;
            PERMUTE3(f, h, g);
            s += 20;
        } while (--iters != 0);
        g = Rotate32(g, 11) * c1;
        g = Rotate32(g, 17) * c1;
        f = Rotate32(f, 11) * c1;
        f = Rotate32(f, 17) * c1;
        h = Rotate32(h + g, 19);
        h = h * 5 + 0xe6546b64;
        h = Rotate32(h, 17) * c1;
        h = Rotate32(h + f, 19);
        h = h * 5 + 0xe6546b64;
        h = Rotate32(h, 17) * c1;
        return h;
    }

    // Bitwise right rotate.  Normally this will compile to a single
    // instruction, especially if the shift is a manifest constant.
    static uint64_t Rotate(uint64_t val, int shift) noexcept {
        // Avoid shifting by 64: doing so yields an undefined result.
        return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
    }

    static uint64_t ShiftMix(uint64_t val) noexcept {
        return val ^ (val >> 47);
    }

    static uint64_t HashLen16(uint64_t u, uint64_t v, uint64_t mul) noexcept {
        // Murmur-inspired hashing.
        uint64_t a = (u ^ v) * mul;
        a ^= (a >> 47);
        uint64_t b = (v ^ a) * mul;
        b ^= (b >> 47);
        b *= mul;
        return b;
    }

    static uint64_t HashLen16(uint64_t u, uint64_t v) noexcept {
        const uint64_t kMul = 0x9ddfea08eb382d69ULL;
        return HashLen16(u, v, kMul);
    }

    static uint64_t HashLen0to16(const char *s, size_t len) noexcept {
        if (len >= 8) {
            uint64_t mul = k2 + len * 2;
            uint64_t a = Fetch64(s) + k2;
            uint64_t b = Fetch64(s + len - 8);
            uint64_t c = Rotate(b, 37) * mul + a;
            uint64_t d = (Rotate(a, 25) + b) * mul;
            return HashLen16(c, d, mul);
        }
        if (len >= 4) {
            uint64_t mul = k2 + len * 2;
            uint64_t a = Fetch32(s);
            return HashLen16(len + (a << 3), Fetch32(s + len - 4), mul);
        }
        if (len > 0) {
            uint8_t a = s[0];
            uint8_t b = s[len >> 1];
            uint8_t c = s[len - 1];
            uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
            uint32_t z = len + (static_cast<uint32_t>(c) << 2);
            return ShiftMix(y * k2 ^ z * k0) * k2;
        }
        return k2;
    }

    // This probably works well for 16-byte strings as well, but it may be overkill
    // in that case.
    static uint64_t HashLen17to32(const char *s, size_t len) noexcept {
        uint64_t mul = k2 + len * 2;
        uint64_t a = Fetch64(s) * k1;
        uint64_t b = Fetch64(s + 8);
        uint64_t c = Fetch64(s + len - 8) * mul;
        uint64_t d = Fetch64(s + len - 16) * k2;
        return HashLen16(Rotate(a + b, 43) + Rotate(c, 30) + d, a + Rotate(b + k2, 18) + c, mul);
    }

    // Return a 16-byte hash for 48 bytes.  Quick and dirty.
    // Callers do best to use "random-looking" values for a and b.
    static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(
            uint64_t w, uint64_t x, uint64_t y, uint64_t z, uint64_t a, uint64_t b) noexcept {
        a += w;
        b = Rotate(b + a + z, 21);
        uint64_t c = a;
        a += x;
        a += y;
        b += Rotate(a, 44);
        return std::make_pair(a + z, b + c);
    }

    // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
    static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(const char *s,
                                                                uint64_t a,
                                                                uint64_t b) noexcept {
        return WeakHashLen32WithSeeds(Fetch64(s), Fetch64(s + 8), Fetch64(s + 16), Fetch64(s + 24), a, b);
    }

    // Return an 8-byte hash for 33 to 64 bytes.
    static uint64_t HashLen33to64(const char *s, size_t len) noexcept {
        uint64_t mul = k2 + len * 2;
        uint64_t a = Fetch64(s) * k2;
        uint64_t b = Fetch64(s + 8);
        uint64_t c = Fetch64(s + len - 24);
        uint64_t d = Fetch64(s + len - 32);
        uint64_t e = Fetch64(s + 16) * k2;
        uint64_t f = Fetch64(s + 24) * 9;
        uint64_t g = Fetch64(s + len - 8);
        uint64_t h = Fetch64(s + len - 16) * mul;
        uint64_t u = Rotate(a + g, 43) + (Rotate(b, 30) + c) * 9;
        uint64_t v = ((a + g) ^ d) + f + 1;
        uint64_t w = base_internal::gbswap_64((u + v) * mul) + h;
        uint64_t x = Rotate(e + f, 42) + c;
        uint64_t y = (base_internal::gbswap_64((v + w) * mul) + g) * mul;
        uint64_t z = e + f + c;
        a = base_internal::gbswap_64((x + z) * mul + y) + b;
        b = ShiftMix((z + a) * mul + d + h) * mul;
        return b + x;
    }

    uint64_t CityHash64(const char *s, size_t len) noexcept {
        if (len <= 32) {
            if (len <= 16) {
                return HashLen0to16(s, len);
            } else {
                return HashLen17to32(s, len);
            }
        } else if (len <= 64) {
            return HashLen33to64(s, len);
        }

        // For strings over 64 bytes we hash the end first, and then as we
        // loop we keep 56 bytes of state: v, w, x, y, and z.
        uint64_t x = Fetch64(s + len - 40);
        uint64_t y = Fetch64(s + len - 16) + Fetch64(s + len - 56);
        uint64_t z = HashLen16(Fetch64(s + len - 48) + len, Fetch64(s + len - 24));
        std::pair<uint64_t, uint64_t> v = WeakHashLen32WithSeeds(s + len - 64, len, z);
        std::pair<uint64_t, uint64_t> w = WeakHashLen32WithSeeds(s + len - 32, y + k1, x);
        x = x * k1 + Fetch64(s);

        // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
        len = (len - 1) & ~static_cast<size_t>(63);
        do {
            x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
            y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
            x ^= w.second;
            y += v.first + Fetch64(s + 40);
            z = Rotate(z + w.first, 33) * k1;
            v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
            w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16));
            std::swap(z, x);
            s += 64;
            len -= 64;
        } while (len != 0);
        return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z,
                         HashLen16(v.second, w.second) + x);
    }

    uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed) noexcept {
        return CityHash64WithSeeds(s, len, k2, seed);
    }

    uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0, uint64_t seed1) noexcept {
        return HashLen16(CityHash64(s, len) - seed0, seed1);
    }

}  // namespace tbir::runtime::hash_internal
